Detect Mode Options; Loss Of Signal (Los); Single And Multi Sync - GE VMIACC-5595 Series Installation Manual

2gb/s reflective memory hub assembly

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Operational Software Description

Detect Mode Options

Each Small Form factor Pluggable transceiver module has a LOS signal that goes high

(1) when a SFP transceiver module fails to detect sufficient light within the normal

spectral operating range. For Reflective Memory, the convention has been to treat this

signal as a Signal Detect (not) rather than a Loss of Signal so each SFP's LOS is

inverted and presented in the Signal Detect column of the Ethernet Control and

Status screen. The Yellow LED adjacent to each port labeled SD also corresponds to

the signal detect.

Each port receiver contains circuitry that detects the occurrence of a network

synchronization pattern K28.5 within each period of approximately

15.5µsec. The K28.5 sync pattern occurs between all network packets and occurs

repeatedly while the network is idle. In addition, this circuitry checks the incoming

data stream for a valid running disparity (proper number of zeros (0) and ones (1) in

each pattern), which is necessary for reliable operation. A combination of both valid

sync and valid running disparity are required to constitute a "true" condition.

If the Detect Mode control is set to the Single-Sync setting, then the associated port's

Sync Detect bit will either be set or reset every 15.5µsec depending on the state of this

"true" condition.

If the Detect Mode control is set to the multi sync setting, then the state of the Port

Sync Detect bit will only change on the occurrence of four consecutive "valid" or

"invalid" periods. Until four consecutive "valid" or "invalid" periods do occur, the

state of the Port Sync Detect signal will remain as before.

When Auto mode is selected in the Bypass Control options, and Single-Sync or

Multi-Sync settings are selected, the port will be bypassed if the corresponding

invalid condition occurs.

Due to hardware limitations, the settings of the Detect Mode (LOS, Single-Sync or

Multi-Sync) is done in pairs of ports. The pairs are ports 0 and 1, ports 2 and 3, ports 4

and 5 with ports 6 and 7 together. Changing the Detect Mode for one port of a pair

will also change the Detect Mode for the other port in the pair.

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